Call it Chemistry
by Jen2261
Summary: Finn and Quinn are in the wrong place at the wrong time, or the right time depending on who you ask. Rachel/Puck. Quinn/Finn. Mentions of Quinn/Sam. Oneshot. Rated M for obvious reasons. Warning inside.


**A/N:** Did this for the Glee kink meme. I'm not a Fuinn shipper (I don't really like Finn at all) but the prompt caught my attention. Sorry to you people that wanted relationship-lovey Fuinn, you have to settle for this. Close enough? Yes? No? Also sorry if I switched tenses at any time, I'm working on that. It's a pain in my ass.

**Prompt:** Finn and Quinn are not in an established relationship (maybe Quinn's even still with Sam) but when they find themselves trapped together listening/watching Puck/Rachel they can't help themselves and end up having sex too, while being as discrete as possible.

**Disclaimer:** I don't own Glee or any of the characters mentioned.

**Warning(s)**: Voyeurism

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><p>"Are you going to help me or are you going to sit there and text your boyfriend for the next hour?"<p>

The question makes Quinn roll her eyes but she sighs and sets her phone down. Finn does have a point. She promised him she would stay after school and help him finish his lab book to turn in tomorrow and if she's being completely honest, she hasn't done anything but text sit next to him and text Sam while he worked through the chemistry problems on the assignment paper.

"Fine. What are you stuck on?" she asks, ignoring the buzz of her phone and giving Finn all her attention. Finn frowns and points to a series of numbers and letters.

"What is that? I don't even remember Mr. Barnes going over that" he asks. Quinn rolls her eyes and sighs.

"It's the formula for photosynthesis."

"Photosyn-synth…"

"It's Photosynthesis Finn, the process that coverts carbon dioxide into organic compounds. Mr. Barnes went over it on Monday."

"I don't remember."

"Of course you don't" is Quinn's only reply. She's not surprised in the least. She takes a second to try and remember how she was even attracted to this guy in the first place. Sam has dyslexia and it still doesn't take this long to explain things to him.

"Why do we even need to know this?" Finn asks a few seconds later. Quinn has picked her phone back up and is laughing at something Sam sent. Finn rolls his eyes.

"Because it's on the test" she deadpans. Finn opens his mouth to reply but the sound of the door slamming open cuts him off. Quinn and Finn turn to look at the door and both of their jaws drop at the scene. Puck storms in carrying Rachel, her long legs wrapped around his waist and her hands around his neck. They're connected by their lips and clearly both have their eyes closed.

"Fuck babe" Puck curses as he pulls away. Quinn watches with a raised eyebrow as Puck kicks the door shut behind him as Rachel's lips latch on to his neck. Puck groans and spins around to set Rachel on the teacher's desk, her back to Finn and Quinn. Clearly Puck has his eyes closed as Rachel does… whatever it is she's doing. Finn nor Quinn can really see.

"Lock the door…" Rachel pants, reaching up to grip Puck's mohawk. Puck hums against her mouth then practically sprints around the desk to lock the door. Quinn and Finn sit frozen.

"Do you think they're going to notice us before they-" Quinn slaps her hand over her mouth with wide eyes as Puck pulls Rachel's shirt over her head.

"mmm mm mmmmpf" Finn mumbles behind her hand. Quinn hisses at him to shut up, grabs his shirt and yanks him off the stool until she's kneeling and he's laying, rubbing his ass, on the floor and glaring at her.

"Shut up!" Quinn hisses again, finally releasing his mouth. Finn frowns. They can both hear Rachel whimpering and Puck humming at the front of the room.

"What are we going to do?" Finn whispers as he watches Quinn push past him and crawl carefully to the edge of the lab bench. She peeks around the far leg to the couple at the front of the room and gasps.

Rachel's completely topless and now sitting on the side of the desk, her right side facing Quinn. The blonde can see the peek of her right breasts as she leans back, bracing her weight on her hands pressed against the desk behind her. Puck his kneeling infront of her, his hands are gripping tan thighs and his head is under her skirt. It doesn't take a genius to know what's going on as Rachel cries out, her back arching and her head falling back. Quinn can feel herself getting red from embarrassment but she can't bring herself to tear her eyes away.

"What's going on?" Finn whispers and Quinn feels him press against her back to lean around her and see. "Woah…"

"Shhh! Do you want them to catch us?" Quinn growls at him. Finn frowns.

"Well what are we supposed to do? Just sit here until they finish? I kind of have a lab book to finish and this is not the-"

"Shit! Oh fuck Noah!" Rachel whines. Quinn and Finn both turn to see Rachel's legs thrown over Puck's shoulders and her hands running over his head, gripping his hair tightly.

"Right there… yessss" Rachel hisses. Her back arches even farther and her leg trembles slightly. Quinn's eyes are wide as saucers as she watches, her knuckles turning white from where she's gripping the wood.

"Finn!" she hisses, turning around to glare at him when she feels the all too familiar poking near her lower back. He has the nerve to blush.

"Sorry Quinn but…" he makes a motion to the scene in front of hm. Quinn rolls her eyes and turns back to look at the couple. Rachel is whimpering and her chest his heaving, Puck is moving faster under her skirt.

"Oh God, oh God, oh God" spills from Rachel's lips and before she can repeat the words a forth time she moaning, gasping and screaming all at the same time as she arches towards Puck's mouth, pulling on his hair for dear life.

"Wow" Finn whispers and Quinn can feel the poking now more than ever. She'd be lying if she said the scene in front of her and the larger than average bulge pressing against her back wasn't making her wet, but unlike Rachel and Puck… she'd wait until she got home.

"Mmm you taste delicious baby" Puck hums as he pulls himself away from the apex of Rachel's thighs. He smirks as his girlfriend lays on the teacher's desk topless, her skin flushed and eyes closed as she pants. Puck licks his lips then crawls over her before pressing his lips to hers, swallowing the moan she releases at tasting herself on his tongue.

"Great. They've had their fun and now they can leave" Quinn says sighing and moving away from Finn and making her way to stand up.

"Not so fast!" Finn whispers, grabbing her arm and yanking her back down. The momentum catches them both off guard and she falls backwards right ontop of him. They both freeze when they hear a gasp.

"Noah? Did you hear that?"

"Hear what babe?" his voice his muffled like his lips are pre-occupied.

"You didn't hear… never mind."

Quinn forces Finn to stay still for a few more seconds until they hear Rachel whimper again. When she's sure they haven't been discovered she sits up. She can barely stop the whimper when she feels the bulge press into her center through her panties, her dress flowing around her and no longer acting as a barrier.

"Uh Quinn…" Finn whispers and Quinn clenches her eyes shut. She knows its because he can feel the heat radiating off her. He may be dumb but he wasn't that dumb.

"Shut up… it doesn't mean anything" she glares at him from over her shoulder. He arches an eyebrow up at her but doesn't say anything. A grunt brings both of their attention back to Puck and Rachel who they'd forgot for a second. Clambering off of Finn, Quinn crawls back to the edge of the desk and peeks around.

The scene makes her whimper and the muscles in her center clench onto something that's not there. Rachel is on her knees, completely naked and facing the back of the room, where Finn and Quinn are trapped. Puck his behind her, his hands braced on her hips. Rachel's right hand his covering his while her left his wrapped around his neck behind her. Their lips are connected to obviously muffle their moans, preventing either of them from noticing the other two in the room.

"Oh God…" Quinn whispers, her eyes tracing Rachel's arched body down to her v between her legs. Her knees are spread enough that Quinn is able to see Puck sliding in and out of the small brunette. The light hitting the couple just right for Quinn to see the wetness spilling out of Rachel, onto her thighs and the desk underneath her.

"Oh God what?" is Finn's question as he moves behind her again to take a look. Fortunately he presses just right against Quinn for the bulge to once again make contact with her center and she whimpers again. Finn frowns and leans down to look at her face.

"Are you okay?"

"No." before he can ask why not she's spinning around and pushing him away from her. Finn falls backwards onto his back and stares at Quinn like she just sprouted 3 heads.

"What the h-mmf" Quinn's mouth is on his instantly and it takes Finn exactly 4 seconds before he's wrapping his arms around her and kissing her back. He kisses her like he used to as she presses her body closer to his. The kiss doesn't last long and she's ripping her lips away to push up his shirt soon enough. He's staring at her wide-eyed.

"Quinn what are you-"

"Shut up!" she hisses, stopping when she's pushed his shirt high enough to expose his stomach and obviously give herself room.

"Oh fuck…" Puck curses from the front of the room, followed by a loud moan from Rachel. That only seems to spur Quinn on more because the next thing she and Finn know, she's unzipping his jeans, reaching inside the front of his boxers and pulling his cock out. She moans softly when it springs free, already at attention and ready to do what she desperately needs it to.

"Quinn what about Sam?" Finn mumbles. Sam should be the last thing he should be thinking about when Quinn his gripping his rock hard cock in her hand and his eyes are rolling in the back of his head but…. He has no reason. Why is he thinking about Sam.

Quinn doesn't reply. She doesn't even acknowledge that she heard him. She simply runs her thumb over the tip, gathering enough moisture to slide her hand along his length comfortably. Finn groans softly, careful not to alert the other couple who probably wouldn't hear him anyway.

Quinn pauses long enough to lean back and peek around the table. Puck and Rachel have switched positions. Puck's laying across the desk and Rachel's straddling him, riding him. Quinn watches as her hips move up and down ontop of him as she leans forward and kisses his. Puck's hand are running up and down her back as he grunts into her mouth. She's never seen anything harder.

"Q-Quinn…" Finn's voice brings her back to the situation in her hand, literally and she watches as his breaths come quicker. No, she did not need his 'early arrival' problem hitting before she got what she needed.

"No." she stops her hand and Finn takes a deep breath, his eyes opening slightly to look up at her.

"What are you doing?" he mumbles through his sex-induced haze.

"You're going to make me cum. If I've got to sit here and listen to Rachel and Puck fuck each other in oblivion, I'm getting off too" she explains, moving over him, her knees braces on either side of his hips. He watches as she uses one hand to reach down and move her panties out the way and the other to grip him. His breath nearly leaves him when he feels the tip slide into her before the rest of him eases into her tight warmth until their pelvis to pelvis.

"Q-Quinn…. Condom" Finn manages to mumble. Quinn bites her lip and shakes her head, mumbling something about birth control.

She throws her head back and reaches to brace her hands on his stomach. His hands connect to her lips as they both lay there just to experience the feeling. It doesn't take long before that's no longer enough and Quinn's hips shift. Finn's mouth drops open in a silent gasp and his hands tighten then she's moving. She moving ontop of him slowly, then faster, then faster.

They're both thankful for the grunts and moans coming from Puck and Rachel still to cover up their own. Finn opens his eyes when he feels Quinn clench around him and she frowns down at him. He arches his eyebrow when she completely stops.

"What?" he asks breathless.

"Harder" is her only response. Finn looks confused so she expands, leaning down to glare directly in his eyes.

"Listen to me, we're not Puck and Rachel. We're not a couple and we're not making love. I want you to fuck me, get me off and then we can get the fuck out of here" she whispers. Finn gives her a blank look and she sighs.

"I should have known you couldn't do this" she sits up and Finn can feel her moving to get off. No way, that's not happening when he's 'this' close to coming. He reaches up, gripping her hips probably harder than necessary and slams her back down on him hard. She gasps, her back arching as she hisses a 'yes' between her teeth. She wants hard? Finn will give her hard.

Before she can comprehend what's happening the worlds is spinning and she's on the floor, her back pressed against the cold floor and Finn his hovering over her with a determined look on his face. She smirks, reaching up and yanks him down by the shirt so her lips are near his ear.

"Fuck me" she whispers, moaning against it when she feels him twitch inside her. That's all it takes before he pounding into her hard enough that she knows she'll probably have bruises on her ass later. When he hits that spot inside her she moans loudly and Finn kisses her to shut up. Apparently its just the right angle because she's just moaning loud against his mouth.

He can't tell in his sex-induced haze if Rachel and Puck are even still in the room. He kisses her harder and she digs her nails into his shoulders when he lifts her leg up to rest in the crook of his arm, the other one wrapped around his waist. He's close, he can feel it building inside his stomach and from the way she's clenching her muscles around him he can tell she is too. He rips his mouth away from hers just in time to gasp. He twitches inside her once, twice before he's coming and he's coming hard. The feeling of him exploding pushes her over the edge and with a hard bite to his shoulder a small whimper she's seeing stars.

They both pant against each other's neck, Finn's hands braced against the floor and Quinn's against his shoulders. Quinn recovers first and pushes Finn away from her. Finn gets the picture and rolls off of her so they're laying shoulder to shoulder.

"That was quite a show, not as good as ours apparently but not fucking bad" the voice makes them both snap their eyes open. Puck is grinning down at them and Rachel is standing next to him, giggling behind her hand.

"Shit dude!" Finn curses, quickly moving to tuck himself inside his jeans as Quinn rearranges her dress. Puck just chuckles.

"You guys really need to learn how to control your horny. This is a school for fuck's sake" Puck shakes his head, Rachel giggles again and then they're gone. Finn groans and sits up, Quinn soon follows and they both look at each other. Before either can say anything Lucky blares from Quinn's phone

"Sam's calling."Finn smirks. Quinn glares.


End file.
